The term elastomer typically refers to ductile tough polymers that frequently have high elasticity. Most elastomers were developed as a cost competitive substitute for vulcanized natural rubber or were formulated to meet a specific property requirement found lacking in natural rubber.
Silicone and organic rubbers are both excellent examples of elastomers. Organic rubbers are long-chain molecules based on a polymer chain of carbon atoms. Silicone polymers are based on a polymer of silicon atoms. Both organic and silicone elastomers often have complex side-chain substitutions to enhance specific properties, but it is the elastomer's polymeric backbone that dominates in performance. Silicone has quartz as a precursor material and organic rubber has petroleum. Silicone elastomers exhibit the widest operating temperature range of any elastomer. Silicones will easily retain their elastomeric properties from −120° F. to +450° F. Organics, on the other hand, have an blastomeric operating temperature range from about −30° F. to +300° F.
The nature of the silicone backbone results generally in superior temperature resistance at all ranges compared to organic elastomers. Silicone based elastomers include rubber and fluorosilicone rubbers. The term silicone rubber can include but is not limited to a variety of materials including room temperature vulcanization (RTV) silicone rubbers, high temperature vulcanization (HTV) silicone rubbers, and low temperature vulcanization (LTV) silicone rubbers. These rubbers are known and are readily available commercially such as SILASTIC®735 black RTV and SILASTIC®732 RTV, both available from Dow Corning, and 106 RTV Silicone Rubber and 90 RTV Silicone Rubber, both available from General Electric. Other suitable silicone materials include the silanes, siloxanes, such as fluorosilicones, dimethylsilicones, liquid silicone rubbers, such as vinyl crosslinked heat curable rubbers or silanol room temperature crosslinked materials, and the like. Other silicone rubbers can include polydimethylsiloxanes and copolymers of ethylene and vinyl dimethylsiloxanes, organic polysiloxane compositions in which the organic polysiloxane is linear or branched, and optionally may contain, in addition to the hydrocarbon groups, certain reactive groups such as for example, hydroxil, hydrolyzable groups, alkenyl groups such as vinyl, hydrogen, fluor, and phenyl. Fluorosilicone rubbers typically include polymethyltrifluoroproplysiloxanes, such as SYLON Fluorosilicone FX11293 and FX11299 sold by 3M.
Although silicone elastomers have better thermal properties than organic elastomers, 450° F. is not very high. As a result, there are applications where silicone elastomers can not be used successfully. Thus, there is a need for silicone elastomer compositions that retain their properties at higher temperatures without thermal degradation. There is also a need for silicone elastomer blends that exhibit superior chemical resistance.